Spintronic THz Wave Emitter: an approach from Topological Weyl Semimetal Heusler alloys

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To achieve the research objectives, I investigated the THz emission from Weyl Heusler alloys Co2MnGa. I have obtained systematic data for the THz emission in Co2MnGa with different chemical ordering. According to the past research it was believed that in a single layer ferromagnet (not Weyl semimetals) the laser-excited electrons inside the ferromagnetic layer generates a back-flow current due to back scattering from substrate or capping layer which emits a THz wave due to anomalous Hall effect (AHE). Such back-scattering process strongly depends on the structural properties like thickness, roughness, and etc. Thus, I also focused on thickness dependence of the THz emission from Co2MnGa films to gain insight into the mechanism of the back scattering-induced THz emission via AHE. For thin regime of Co2MnGa films grown on MgO substrates and capped by the MgO layers, I found the strong signature that the origin of the THz emission was AHE which was enhanced by Weyl nature in Co2MnGa. In addition, I have investigated the composition dependence of the THz emission of Co2MnGa to clarify how the Wyle point location with respect to the Fermi level influences the THz emission. Those results were discussed in several conference meetings and the paper was submitted.